Image lens with high resolution and small distance

ABSTRACT

An image lens, in the order from the object side to the image side thereof, includes a first lens including a first surface and a second surface, a second lens including a third surface and a fourth surface, a third lens including a fifth surface and a sixth surface, a fourth lens including a seventh surface and a eighth surface, a fifth lens including a ninth surface and a tenth surface, and an image plane. The image lens satisfies the following formulas: (1) D/TTL&gt;0.94; (2) D/L&gt;1.21; wherein D is the maximum image diameter of the image plane; TTL is a total length of the image lens, and L is a distance from an outmost edge of the tenth surface to an optical axis of the image lens along a direction perpendicular to the optical axis.

BACKGROUND

1. Technical Field

The present disclosure relates to lenses and, particularly, to an imagelens with high resolution and small distance.

2. Description of Related Art

Image sensors are used to capture an image. A size of an image sensor,such as a complementary metal oxide semiconductor device (CMOS),decreases with development of technology. For proper matching with theimage sensor, an image lens, which is essentially comprised of a numberof lenses, should be able to meet requirements, such as, high resolutionand small distance. However, the existing image lenses cannot meet theserequirements, thus, results in poor imaging effect.

Therefore, it is desirable to provide an image lens which can overcomethe limitations described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an image lens in accordance with thepresent disclosure.

FIGS. 2˜5 are graphs respectively showing spherical aberration, fieldcurvature, distortion, and characteristic curves of modulation transferfunction occurring in the image lens, that is in a telephoto state,according to a first exemplary embodiment.

FIGS. 6˜9 are graphs respectively showing spherical aberration, fieldcurvature, distortion, and characteristic curves of modulation transferfunction occurring in the image lens, that is in a wide-angle state,according to the first exemplary embodiment.

FIGS. 10˜13 are graphs respectively showing spherical aberration, fieldcurvature, distortion, and characteristic curves of modulation transferfunction occurring in the image lens, that is in a telephoto state,according to a second exemplary embodiment.

FIGS. 14˜17 are graphs respectively showing spherical aberration, fieldcurvature, distortion, and characteristic curves of modulation transferfunction occurring in the image lens, that is in a wide-angle state,according to the second exemplary embodiment.

DETAILED DESCRIPTION

Embodiments of the disclosure will now be described in detail withreference to the accompanying drawings.

FIG. 1, shows an image lens 100, according to an exemplary embodiment,optically capturing an image of an object at an object side and forminga corresponding image on an image plane 20. The image lens 100 includes,in an order from the object side to the image side, a first lens L1 withpositive refraction power, a second lens L2 with negative refractionpower, a third lens L3 with positive refraction power, a fourth lens L4with positive refraction power, a fifth lens L5 with negative refractionpower, and IR-cut filter 10.

The first lens L1 includes a convex first surface S1 facing the objectside and a convex second surface S2 facing the image side.

The second lens L2 includes a convex third surface S3 facing the objectside and a concave fourth surface S4 facing the image side.

The third lens L3 includes a convex third surface S5 facing the objectside and a convex sixth surface S6 facing the image side.

The fourth lens L4 includes a concave seventh surface S7 facing theobject side and a convex eighth surface S8 facing the image side.

The fifth lens L5 includes a concave ninth surface S9 facing the objectside and a concave tenth surface S10 facing the image side.

The IR-cut filter 10 includes an eleventh surface S11 facing the objectside and a twelfth surface S12 facing the image side.

The image lens 100 further includes an aperture stop 30. The aperturestop 30 is positioned between the first lens L1 and the second lens L2.Light rays enter the image lens 100, passing through the first lens L1,the aperture stop 30, the second lens L2, the third lens L3, the fourthlens L4, the fifth lens L5, and the IR-cut filter 10, finally formingoptical images on the image plane 20. The aperture stop 30 is foradjusting light flux from the first lens L1 to the second lens L2. Inaddition, the aperture stop 30 facilitates uniform light transmissionwhen light passes through the first lens L1 to correct coma aberrationsof the image lens 100. The IR-cut filter 10 filters/removes infraredlight from the light rays.

The image lens 100 satisfies the formulas:D/TTL>0.94;  (1)D/L>1.21;  (2)

wherein D is the maximum image diameter of the image plane 20; TTL is atotal length of the image lens 100; L is a distance from an outmost edgeof the tenth surface S10 to an optical axis of the image lens 100 alonga direction perpendicular to the optical axis of the image lens 100.

The formulas (1) to (2) are for shortening the length of the image lens100, and reducing the aberration of the field curvature and sphericalaberration in the zoom process. If the image lens 100 does not satisfythe formulas (1) to (2), the distance of the image lens 100 cannot bemaintained and the images captured by the image lens 100 cannot becorrected.

The image lens 100 further satisfies the formula:Z/Y>0;  (3)

wherein Z is a distance from a central point of the seventh surface S7to an outmost edge of the eighth surface S8 along the optical axis, Y isa distance from an outmost edge of the eighth surface S8 to the opticalaxis along a direction perpendicular to the optical axis.

Formula (3) is for properly distributing the refraction power, whilemaintaining a relatively small spherical aberration.

The image lens 100 further satisfies the formulas:R31/F3>R11/F1>0;  (4)R12/F1<R32/F3<0;  (5)

wherein R11 is the curvature radius of the first surface S1 of the firstlens L1; R12 is the curvature radius of the second surface S2 of thefirst lens L1; R31 is the curvature radius of the fifth surface S5 ofthe third lens L3, R32 is the curvature radius of the sixth surface S6of the third lens L3; F1 is focal length of the first lens L1, and F3 isfocal length of the third lens L3.

Formulas (4)-(5) are for maintaining quality of images captured by theimage lens 100. If the image lens 100 does not satisfy the formulas (4)to (5), the images captured by the image lens 100 cannot be corrected.

The image lens 100 further satisfies the formulas:R51/F5<R52/F5<0;  (6)

wherein R51 is the curvature radius of the ninth surface S9 of the fifthlens L5; R52 is the curvature radius of the tenth surface S10 of thefifth lens L5; F5 is focal length of the fifth lens L5.

Formula (6) is for correcting chromatic aberration of the image lens100. If the image lens 100 does not satisfy the formula (6), the imagescaptured by the image lens 100 will have a greater chromatic aberration.

All of the first, second, third, fourth, fifth, sixth, seventh, eighth,ninth, tenth surfaces S1, S2, S3, S4, S5, S6, S7, S8, S9 and S10 areaspherical surfaces. Each aspherical surface is shaped according to theformula:

$Z = {\frac{{ch}^{2}}{1 + \sqrt{1 - {\left( {k + 1} \right)c^{2}h^{2}}}} + {\sum{A_{i}h^{i}}}}$

wherein Z is the length of a line drawn from a point on the asphericalsurface to the tangential plane of the aspherical surface, h is theheight from the optical axis to the point on the aspherical surface, cis a vertex curvature (=1/R, the radius of curvature), k is a conicconstant, and Ai are the correction coefficients, to the order of “i” ofthe aspherical surface.

Detailed examples of the imaging lens 100 are given below in accompanywith FIGS. 2-17, but it should be noted that the imaging lens 100 is notlimited by these examples. Listed below are the symbols used in thesedetailed examples:

FNo: F number;

2ω: field angle;

ri: radius of curvature of the surface Si;

Di: distance between surfaces on the optical axis of the surface Si andthe surface Si+1;

Ni: refractive index of the surface Si;

Vi: Abbe constant of the surface Si;

Ki: Secondary curvature of the surface Si.

Example 1

Tables 1-4 show a first embodiment of the image lens 100.

TABLE 1 ri Di Surface type (mm) (mm) ni Vi ki first surface S1aspherical 2.10 0.70 1.53 56.0 −0.54 second surface S2 aspherical −10.410.05 — — — aperture stop 30 standard Infinity 0.03 — — — third surfaceS3 aspherical 5.41 0.41 1.63 23.4 −58.69  fourth surface S4 aspherical1.80 0.33 — — −0.33 fifth surface S5 aspherical 9.69 0.64 1.53 56.0 —sixth surface S6 aspherical −7.51 0.45 — — — seventh surface S7aspherical −1.82 0.60 1.53 56.0 −3.64 eighth surface S8 aspherical −0.980.20 — — −3.15 ninth surface S9 aspherical 15.00 0.58 1.53 56.0 — tenthsurface S10 aspherical 1.25 0.65 — — −7.68 eleventh surface S11 standardInfinity 0.30 1.52 58.6 — twelfth surface S12 standard Infinity 0.54 — —— image plane 20 standard — — — — —

TABLE 2 aspherical first second third fourth fifth coefficient surfaceS1 surface S2 surface S3 surface S4 surface S5 A4 5.6E−03 0.0171−3.5E−03 −0.0865 −0.0417 A6 −4.2E−03 0.0159 0.0403 0.0969 −0.0121 A81.5E−03 −0.0154 −5.7E−03 −0.0452 0.0271 A10 3.3E−03 −0.0139 −0.05583.6E−04 −2.2E−03 A12 −3.4E−03 8.2E−03 0.0246 5.8E−04 −1.9E−04 A14−1.5E−04 5.9E−04 8.0E−03 2.2E−04 −1.2E−03

TABLE 3 aspherical sixth seventh eighth ninth tenth coefficient surfaceS6 surface S7 surface S8 surface S9 surface S10 A4 −0.0274 −0.0165−0.0600 −0.0860 −0.0643 A6 −8.5E−03 −0.0132 0.0168 3.0E−03 0.0156 A8−0.0122 −1.7E−03 4.9E−04 6.1E−03 −3.1E−03 A10 7.9E−03 2.0E−03 −2.6E−04−1.8E−03 1.7E−04 A12 7.2E−06 −4.7E−06 3.3E−05 −2.2E−04 2.6E−05 A141.4E−05 −8.5E−06 −4.5E−06 6.7E−05 −4.1E−06

TABLE 4 F(mm) F/No 2ω 4.44 2.50 66.21°

In the embodiment, D=5.867 mm; TTL=5.48 mm; Z=0.137 mm; Y=1.45 mm;L=4.47 mm; F1=3.32; F3=7.99 mm; F5=−2.57 mm.

FIGS. 2-5 are graphs of aberrations (spherical aberration, fieldcurvature, distortion, and characteristic curves of modulation transferfunction occurring in the first exemplary embodiment of the image lens100 in a telephoto state. FIGS. 6-9, are graphs of aberrations(spherical aberration, field curvature, distortion, and lateralchromatic aberration) of the first exemplary embodiment of the imagelens 100 in a wide angle state. In FIGS. 2 and 6, curves are sphericalaberration characteristic curves of F light (wavelength: 486 nm), dlight (wavelength: 588 nm) and C light (wavelength: 654 nm) of the imagesystem 100. The spherical aberration of the image lens 100 of the firstexemplary embodiment is from −0.05 mm to 0.05 mm. As illustrated inFIGS. 3 and 7, the curves T and S are respectively the tangential fieldcurvature curve and the sagittal field curvature curve. The fieldcurvature of the first exemplary embodiment of the image lens 100 isfrom −0.05 mm to 0.05 mm. In FIGS. 4 and 8, the distortion of the firstexemplary embodiment of the image lens system 100 is from −2.00% to2.00%. Furthermore, as shown in FIG. 5, for half of the Nyquistfrequency (about 2241 p/mm), the MTF of the central field is greaterthan 55% (see curve mc), the MTF of the 0.8 field is greater than 40%(see curve mp), the MTF between the central field and the 0.8 field isin a range of: 40%˜55% (see curve mt, for example). As shown in FIG. 9,for half of the Nyquist frequency (about 2241 p/mm), the MTF of thecentral field is greater than 42% (see curve mc). The MTF of the 0.8field is greater than 14% (see curve mp). The MTF between the centralfield and the 0.8 field is in a range of: 14%˜42% (see curve mt, forexample).

Example 2

Tables 5-8 show a second embodiment of the image lens 100.

TABLE 5 ri Di Surface type (mm) (mm) ni vi ki first surface S1aspherical 2.14 0.52 1.53 56.0  0.42 second surface S2 aspherical −15.530.07 — — −58.87  aperture stop 30 standard Infinity 0.06 — — — thirdsurface S3 aspherical 5.69 0.39 1.63 23.4 — fourth surface S4 aspherical1.88 0.35 — — −7.00 fifth surface S5 aspherical 7.16 0.58 1.53 56.0 —sixth surface S6 aspherical −9.75 0.41 — — — seventh surface S7aspherical −1.89 0.70 1.53 56.0 — eighth surface S8 aspherical −0.980.25 — — −2.80 ninth surface S9 aspherical 423.22 0.58 1.53 56.0 — tenthsurface S10 aspherical 1.41 0.25 — — −8.33 eleventh surface S11 standardInfinity 0.30 1.52 58.6 — twelfth surface S12 standard Infinity 1.07 — —— image plane 20 standard — — — — —

TABLE 6 aspherical first second third fourth fifth coefficient surfaceS1 surface S2 surface S3 surface S4 surface S5 A4 −3.3E−03 8.1E−03−0.0769 9.4E−03 −0.0589 A6 1.9E−03 0.0370 0.1175 0.0456 0.0127 A8−4.1E−03 −0.0326 −0.0963 −0.0436 −9.0E−03 A10 8.3E−03 7.4E−03 0.01070.0261 0.0213 A12 −3.8E−03 3.3E−06 0.0117 −0.0116 −6.1E−03

TABLE 7 sixth seventh eighth ninth tenth aspherical surface surfacesurface surface surface coefficient S6 S7 S8 S9 S10 A4 −0.0281 0.0266−0.0672 −0.0682 −0.0679 A6 −9.0E−03 −4.9E−03 0.0131 −6.0E−03 0.0184 A81.5E−03 −1.5E−03 2.5E−03 9.9E−03 −4.8E−03 A10 −2.0E−03 1.5E−03 −1.7E−03−4.3E−03 6.5E−04 A12 3.3E−03 −4.9E−06 4.2E−04 5.5E−04 −4.2E−05

TABLE 8 F(mm) F/No 2ω 4.52 2.51 65.43°

In the embodiment, D=5.867 mm; TTL=5.66 mm; Z=0.121 mm; Y=1.44 mm;L=4.42 mm; F1=3.55 mm; F3=7.78 mm; F5=−2.63 mm.

FIGS. 10-13 are graphs of aberrations (spherical aberration, fieldcurvature, distortion, and characteristic curves of modulation transferfunction occurring in the image lens 100) of the second exemplaryembodiment of the image lens 100 in the telephoto state. FIGS. 14-17 aregraphs of aberrations (spherical aberration, field curvature,distortion, and lateral chromatic aberration) of the second exemplaryembodiment of the image lens 100 in the wide angle state. In FIGS. 10and 14, curves are spherical aberration characteristic curves of F light(wavelength: 486 nm), d light (wavelength: 588 nm) and C light(wavelength: 654 nm) of the image system 100. The spherical aberrationof the image lens 100 of the second exemplary embodiment is from −0.05mm to 0.05 mm. As illustrated in FIGS. 11 and 15, the curves T and S arerespectively the tangential field curvature curve and the sagittal fieldcurvature curve. The field curvature of the second exemplary embodimentof the image lens 100 is from −0.05 mm to 0.05 mm. In FIGS. 12 and 16,the distortion of the second exemplary embodiment of the image lenssystem 100 is from −2.00% to 2.00%. Furthermore, as shown in FIG. 13,for half of the Nyquist frequency (about 2241 p/mm), the MTF of thecentral field is greater than 55% (see curve mc), the MTF of the 0.8field is greater than 40% (see curve mp), the MTF between the centralfield and the 0.8 field is in a range of: 40%˜55% (see curve mt, forexample). As shown in FIG. 17, for half of the Nyquist frequency (about2241 p/mm), the MTF of the central field is greater than 42% (see curvemc), the MTF of the 0.8 field is greater than 14% (see curve mp), theMTF between the central field and the 0.8 field is in a range of:14%˜42% (see curve mt, for example). Overall, in this embodiment, thespherical aberration, the field curvature, the distortion, and the chiefray angle are limited in a small range.

Particular embodiments are shown and described by way of illustrationonly. The principles and the features of the present disclosure may beemployed in various and numerous embodiments thereof without departingfrom the scope of the disclosure as claimed. The above-describedembodiments illustrate the scope of the disclosure but do not restrictthe scope of the disclosure.

What is claimed is:
 1. An image lens, in the order from an object sideto an image side thereof, comprising: a first lens having positiverefraction power and comprising a first surface facing the object sideand a second surface facing the image side; a second lens havingnegative refraction power and comprising a third surface facing theobject side and a fourth surface facing the image side; a third lenshaving positive refraction power and comprising a fifth surface facingthe object side and a sixth surface facing the image side; a fourth lenshaving positive refraction power and comprising a seventh surface facingthe object side and a eighth surface facing the image side; a fifth lenshaving negative refraction power and comprising a ninth surface facingthe object side and a tenth surface facing the image side; and an imageplane; wherein the image lens satisfies the following formulas:D/TTL>0.94;  (1)D/L>1.21;  (2) wherein D is the maximum image diameter of the imageplane; TTL is a total length of the image lens, L is a distance from anoutmost edge of the tenth surface to an optical axis of the image lensalong a direction perpendicular to the optical axis of the image lens;wherein the image lens further satisfies the formulas:Z/Y>0; and  (3) wherein Z is a distance from a central point of theseventh surface to an outmost edge of the eighth surface along theoptical axis, Y is a distance from an outmost edge of the eighth surfaceto the optical axis along a direction perpendicular to the optical axis.2. The image lens as claimed in claim 1, wherein the image lens furthersatisfies the formulas:R31/F3>R11/F1>0;  (4)R12/F1<R32/F3<0;  (5) Wherein R11 is the curvature radius of the firstsurface of the first lens; R12 is the curvature radius of the secondsurface of the first lens; R31 is the curvature radius of the fifthsurface of the third lens, R32 is the curvature radius of the sixthsurface of the third lens; F1 is focal length of the first lens, and F3is focal length of the third lens.
 3. The image lens as claimed in claim2, wherein the image lens further satisfies the formulas:R51/F5<R52/F5<0;  (6) Wherein R51 is the curvature radius of the ninthsurface of the fifth lens; R52 is the curvature radius of the tenthsurface of the fifth lens; F5 is focal length of the fifth lens.
 4. Theimage lens as claimed in claim 3, wherein the first, second, third,fourth, fifth, sixth, seventh, eighth, ninth, tenth surfaces areaspherical surfaces.
 5. The image lens as claimed in claim 4, whereinthe first surface is a convex surface facing the object side, the secondsurface is a convex surface facing the image side, the third surface isa concave surface facing the object side, and the fourth surface is aconcave surface facing the image side, the fifth surface is a convexsurface facing the object side, the sixth surface is a convex surfacefacing the image side, the seven surface is a concave surface facing theobject side, the eighth surface is a convex surface facing the imageside, the ninth surface is a concave surface facing the object side, thetenth surface is a concave surface facing the image side.
 6. The imagelens as claimed in claim 5, wherein the image lens further comprises anaperture stop positioned between the first lens and the second lens. 7.The image lens as claimed in claim 6, further comprising an IR-cutfilter, wherein the IR-cut filter is positioned between the fifth lensand the image plane.